European Published Patent Application No. 0 875 730 and German Published Patent Application No. 698 15 940 describe a map data display device for use in a vehicle navigation device having a data-conversion device for recording points of map data according to a map, from a viewpoint through a viewing line originating from the viewpoint and having an angle of depression with respect to the plane of the map, and for perspectively projecting the points of the map data onto a viewing plane, which is fixed perpendicularly to the viewing line and is a predefined distance from the location, in order to generate map display data. This produces a bird's-eye view of an environment. A navigation system having a bird's-eye view of an environment is also described in French Published Patent Application No. 2 634 707 and the periodical AUTOCONNECT 2005, Vereinigte Motor-Verlage GmbH & Co. KG (United Motor Publishing House, Inc.), Leuschnerstr. 1, 70174 Stuttgart, Federal Republic of Germany, pages 18 and 21.
European Published Patent Application No. 0 990 119 describes a digital personal communication device having a processor, a memory that the processor can access, and a display that is connected to the processor. The display displays map data and a position of the digital personal communication device with respect to the map data, and the map data includes route points, i.e., coordinates, as instructed by the processor. Furthermore, the digital personal communication device includes an input device for forming queries for map information and for selecting route points, and a GPS receiver that is connected to the processor. The processor is programmed to process data it receives from the GPS receiver such that the position of the digital personal communication device is able to be determined from the data. Moreover, the digital personal communication device includes a transmitter that is connected to the processor, the processor programmed such that, utilizing the transmitter, it requests map data from a map memory and a transmission device, processes the map information it obtained from the map memory and the transmission device, and determines the availability of additional stored data regarding route points in the memory during the selection of one of the route points by the input device, and, using the transmitter, it requests additional stored data from the map memory and the transmission device during the selection of one of the route points if additional, stored data are not available in the memory.